快冷微晶钐铁合金微观结构及渗氮行为
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摘要
采用快速凝固技术可制备出综合性能优于铸造状态的微晶合金,利用真空旋淬炉制备出了不同冷却速度下的钐铁合金,研究了其显微组织结构和相构成演变规律,并对其进行了氮化处理。结果表明,随着快冷速率的增加,合金中元素偏析程度降低,组织特征呈现粗大树枝晶粒向微晶的演变,当辊速达到24.0m/s时,可得到微晶钐铁合金。在420℃对微晶钐铁合金直接进行氮化处理,其晶粒长大倾向很小。晶粒细小,晶界面积增大,使得有效渗氮点增多,促进了氮原子的扩散,但氮原子主要以含氮化合物的形式分布在晶粒的边界,导致了晶界与晶粒内部的氮化不均匀。
Micro-crystalline alloys which produced by rapid solidification technologies could have better properties than as-cast alloys.Some Sm-Fe alloys were prepared under different cooling rates in the vacuum rotary quenching furnace.The microstructure and phase composition of the microstructure were studied and gas nitridation was carried out.The results show that with the increase of rapid cooling rate,the segregation of elements in the alloy decreases,and the microstructure of the alloy changes from coarse dendrite to microcrystalline.When the cooling rate reached to 24.0 m/s,the alloy with a microcrystalline microstructure could be obtained.The grain growth tendency of microcrystalline Sm-Fe alloy is very small under the condition of direct nitriding of the alloy at 420℃.The grain size is small and the grain boundary area increases,which makes the effective nitriding points increase and promotes the diffusion of nitrogen atoms.However,nitrogen atoms are mainly distributed at grain boundaries in the form of nitrogen compounds,resulting in uneven nitridation between grain boundaries and grain interiors.
Micro-crystalline alloys which produced by rapid solidification technologies could have better properties than as-cast alloys.Some Sm-Fe alloys were prepared under different cooling rates in the vacuum rotary quenching furnace.The microstructure and phase composition of the microstructure were studied and gas nitridation was carried out.The results show that with the increase of rapid cooling rate,the segregation of elements in the alloy decreases,and the microstructure of the alloy changes from coarse dendrite to microcrystalline.When the cooling rate reached to 24.0 m/s,the alloy with a microcrystalline microstructure could be obtained.The grain growth tendency of microcrystalline Sm-Fe alloy is very small under the condition of direct nitriding of the alloy at 420℃.The grain size is small and the grain boundary area increases,which makes the effective nitriding points increase and promotes the diffusion of nitrogen atoms.However,nitrogen atoms are mainly distributed at grain boundaries in the form of nitrogen compounds,resulting in uneven nitridation between grain boundaries and grain interiors.
引文
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[5]赵平,赵国际.急冷快淬工艺对Sn-9Zn-0.5Ag焊料组织与熔化特性的影响[J].热加工工艺,2017,46(1):218-220.
[6]方正,秦林,丁俭,等.快速凝固Al-Ti-B-Sc对A356.2铝合金的晶粒细化作用[J].河北工业大学学报,2014,43(2):61-65.
[7]ZHOU T,CHEN Z H,YANG M B,et al.Investigation on microstructure characterization and property of rapidly solidified Mg-Zn-Ca-Ce-La alloys[J].Materials Characterization,2012,63:77-82.
[8]WEN L,YUAN Y,WANG Y,et al.Effect of Nanocrystalline surface and iron-containing layer obtained by SMAT on tribological properties of 2024Al Alloy[J].Rare Metal Materials&Engineering,2015,44(6):1 320-1 325.
[9]LIN Y,LU J,WANG L,et al.Surface nanocrystallization by surface mechanical attrition treatment and its effect on structure and properties of plasma nitrided AISI 321stainless steel[J].Acta Materialia,2006,54(20):5 599-5 605.
[10]佟伟平,陶乃镕,王镇波,等.纳米结构纯铁的气体渗氮[J].热处理,2007,22(2):11-14.
[11]DING J,MCCORMICK P G,STREET R.Remanence enhancement in mechanically alloyed isotropic Sm7Fe9 3-nitride[J].Journal of Magnetism&Magnetic Materials,1993,124(1-2):1-4.
[12]KATTER M,WECKER J,SCHULTZ L.Structural and hard magnetic properties of rapidly solidified SmFe-N[J].Journal of Applied Physics,1991,70(6):3 188-3 196.
[13]马建勋,严密,赵传礼,等.氮化前显微组织对SmFeN合金磁性能的影响[J].材料科学与工程学报,2005,23(2):244-247.
[14]CUI C X,ZHANG Y,SUN J B,et al.Fabrication and magnetic properties of Sm3(Fe,Ti)29 Nx/α-Fe dualphase nanocomposite permanent magnetic material[J].Science in China Series E:Technological Sciences.2007(2):184-189.
[15]孙继兵.Sm-Fe与Sm-Fe-M(M=Ti,Nb)合金及其氮化物磁性材料的研究[D].天津:河北工业大学,2004.
[16]张然,刘颖,李芳,等.Sm2Fe17合金的氮化处理及其相关影响[J].磁性材料及器件,2004,35(2):39-41.